RT Journal Article SR Electronic T1 Native CYP2C11: Heterologous Expression in Saccharomyces cerevisiae Reveals a Role for Vacuolar Proteases Rather Than the Proteasome System in the Degradation of This Endoplasmic Reticulum Protein JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1146 OP 1153 DO 10.1124/mol.61.5.1146 VO 61 IS 5 A1 Bernard P. Murray A1 Victor G. Zgoda A1 Maria Almira Correia YR 2002 UL http://molpharm.aspetjournals.org/content/61/5/1146.abstract AB Cytochromes P450 (P450s) are hemoprotein enzymes committed to the metabolism of chemically diverse endo- and xenobiotics. They are anchored to the endoplasmic reticulum (ER) membrane with the bulk of their catalytic domain exposed to the cytosol, and thus they constitute excellent examples of integral monotopic ER proteins. Physiologically they are known to turn over asynchronously, but the determinants that trigger their proteolytic disposal and the pathways for such cellular disposal are not well defined. We recently showed that CYP3A4, the dominant human liver drug-metabolizing enzyme, and its rat liver orthologs undergo ubiquitin-dependent 26S proteasomal degradation not only after suicide inactivation, but also when CYP3A4 is expressed inSaccharomyces cerevisiae, presumably in its “native” form. The latter findings, obtained by the use of strains either with compromised proteasomal degradation of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) or deficient in ubiquitin-conjugating enzymes (Ubc; UBC), revealed that this native monotopic P450 enzyme, in common with the polytopic HMGR, required the function of certain HRD(HMGR degradation) and UBC genes. In this study, we examined the degradation of CYP2C11, a male rat liver–specific P450, by heterologous expression in S. cerevisiae under comparable conditions. We report that unlike CYP3A4 and HMGR, the degradation of CYP2C11 in S. cerevisiae is independent of either HRD or UBC gene function, but it is largely dependent on vacuolar (lysosomal) proteolysis. These findings with two monotopic ER hemoproteins, CYP2C11 and CYP3A4, and the polytopic ER protein HMGR attest to the remarkable mechanistic diversity of cellular proteolytic disposal of ER proteins.